Instrument panels of the type used in automotive applications are often composed of a number of keys or buttons having insignias that identify the particular function of each button. The insignias can be formed in various ways, depending on the application and whether the instrument panel is backlit or not. For example, the insignias can be formed by directly printing an ink onto the displayed surface of the button. Other known methods include forming the insignia during the molding of the button, such as by an in-molded decoration foil or an insert-molded film. Still another method uses conventional paint and laser technologies. This method generally involves forming the button from a white material or painting the surface of the button white, and then coating the surface of the button with an opaque paint so as to conceal the white surface of the button. A portion of the opaque paint is then lased away to expose the underlying white surface of the button, thereby forming an insignia.
Backlit buttons are often employed because of their enhanced visibility at nighttime. Their backlit capability necessitates that they be able to transmit light from a light source behind the instrument panel to the insignia. The manufacture of backlit buttons can be typically accomplished using any of the previously described processes, except that the button must be first molded from a substantially transparent material. Commonly used transparent materials include polycarbonate and acrylic resins.
To affect the manner in which light is transmitted through the button, it is known to disperse various materials within the resin. For example, U.S. Pat. No. 4,729,067 to Ohe teaches a button that includes a transparent substrate and a light diffusing layer composed of an acrylic resin matrix in which is dispersed a light diffusing agent.
While the above manufacturing methods are widely accepted and employed in the art, each has the disadvantage of using hazardous liquid chemicals either directly, such as during the creation of the graphic in the button, or indirectly, such as in the manufacture of an intermediate decoration or insert. For example, paint and laser techniques require a painting operation, and printing techniques require paint-like chemicals, each of which involves the use of solvents and volatile substances that can pose a health hazard. Furthermore, in-mold decoration foils and insert-molded films are manufactured with inks and coatings containing volatile organics that must also be carefully controlled in the manufacturing environment due to their harmful nature.
Another drawback of the processes noted above is that they each tend to complicate the manufacture of a backlit button. For example, printing techniques require dedicated printing equipment and a firing operation. Paint and laser methods require at minimum a coating step and a drying or curing step, while in-mold decoration foils and insert-molded films add an additional step to the molding process. These additional processing steps undesirably contribute to the manufacturing and material costs of a backlit button.
Accordingly, it would be desirable if a process existed by which graphics for backlit buttons could be produced without necessitating the use of hazardous liquid chemistries, coatings, paints or inks. Furthermore, it would be desirable if such a process were relatively uncomplicated, requiring minimal equipment and processing steps to produce a finished backlit button.